feat(dictation): pulse three dots in the pill while spoken words are still on their way (#40443)

* feat(dictation): show pending dots while the engine holds speech it hasn't committed

The VAD pause segmenter already knows when a phrase is open. The recognizer
now posts speech-pending when a phrase opens and clears it once that phrase's
text is posted, and the desktop pill shows three dots after the text while it
is on. Only pause-cut on-device streams send it, so cloud, the paired web
client and phones keep today's pill.

* fix(speech): keep a lone click from turning the pending dots on

src/preload/api/speech-api.ts

@@ -7,6 +7,7 @@ import type {
   SpeechLifecycleEvent,
   SpeechModelManifest,
   SpeechModelState,
+  SpeechPendingEvent,
   SpeechTranscriptEvent
 } from '../../shared/speech-types'
 
@@ -39,6 +40,7 @@ export type SpeechApi = {
   cancelDictation: (sessionId: string) => Promise<void>
   onPartialTranscript: (callback: (data: SpeechTranscriptEvent) => void) => () => void
   onFinalTranscript: (callback: (data: SpeechTranscriptEvent) => void) => () => void
+  onSpeechPending: (callback: (data: SpeechPendingEvent) => void) => () => void
   onDownloadProgress: (
     callback: (data: { modelId: string; progress: number }) => void
   ) => () => void

src/preload/api/speech-bridge.ts

@@ -9,6 +9,7 @@ import type {
   SpeechLifecycleEvent,
   SpeechModelManifest,
   SpeechModelState,
+  SpeechPendingEvent,
   SpeechTranscriptEvent
 } from '../../shared/speech-types'
 import type { PreloadApi } from '../api-types'
@@ -111,6 +112,12 @@ export const speechApi = {
     ipcRenderer.on('speech:final', listener)
     return () => ipcRenderer.removeListener('speech:final', listener)
   },
+  onSpeechPending: (callback: (data: SpeechPendingEvent) => void): (() => void) => {
+    const listener = (_event: Electron.IpcRendererEvent, data: SpeechPendingEvent): void =>
+      callback(data)
+    ipcRenderer.on('speech:pending', listener)
+    return () => ipcRenderer.removeListener('speech:pending', listener)
+  },
   onDownloadProgress: (
     callback: (data: { modelId: string; progress: number }) => void
   ): (() => void) => {